It is known in the art that photographic display materials are utilized for advertising as well as decorative displays of photographic images. Since these display materials are used in advertising, the image quality of the display material is critical in expressing the quality message of the product or service being advertised. Furthermore, a photographic display image needs to be high impact, as it attempts to draw consumer attention to the display material and the desired message being conveyed. Typical applications for display material include product and service advertising in public places such as airports, buses and sports stadiums, movie posters and fine art photography. The desired attributes of a quality, high impact photographic display material are a slight blue density minimum, durability, sharpness and flatness. Cost is also important as display materials tend to be expensive compared with alternative display material technology mainly lithographic images on paper. For display materials, traditional color paper is undesirable as it suffers from a lack of durability for the handling, photographic processing and display of large format images.
In the formation of color paper it is known that the base paper has applied thereto a layer of polymer, typically polyethylene. This layer serves to provide waterproofing to the paper, as well as providing a smooth surface on which the photosensitive layers are formed. The formation of a suitably smooth surface is difficult requiring great care and expense to ensure proper laydown and cooling of the polyethylene layers. The formation of a suitably smooth surface would also improve image quality as the display material would have more apparent blackness as the reflective properties of the improved base are more specular than the prior materials. As the whites are whiter and the blacks are blacker, there is more range in between and, therefore, contrast is enhanced. It would be desirable if a more reliable and improved surface could be formed at less expense.
Prior art photographic reflective papers comprise a melt extruded polyethylene layer which also serves as a carrier layer for optical brightener and other whitener materials as well as tint materials. It would be desirable if the optical brightener and tints, rather than being dispersed a single melt extruded layer of polyethylene could be concentrated nearer the surface where they would be more effective optically.
Prior art photographic clear display materials have light sensitive silver halide emulsions coated directly onto a gelatin coated clear polyester sheet. Clear photographic display materials are typically used as overhead materials that are projected on a screen, typically highly reflective and white and display materials that utilize light boxes with a white diffuser screen. Diffuser screens are necessary to diffuse the light source used to backlight clear display materials and to provide the white portion of the image. Without a diffuser, the light source would significantly reduce the quality of the image. Since light sensitive silver halide emulsions that are used for prior art clear display materials tend to be yellow because of the gelatin used as a binder for photographic emulsions, the minimum density areas of a developed image will tend to appear as a yellow white. A yellow white reduces the commercial value of a transmission display material because the imaging viewing public associates image quality with a blue white. It would be desirable if a clear display material could have a more blue white.
Prior art clear display materials use a high coverage of light sensitive silver halide emulsion coated on one side of the base to increase the density of the image compared to photographic reflective print materials. An increase in dye density is required for clear display materials to provide the required dye density associated with a quality image. While increasing the coverage does increase the density of the image in transmission space, the time to image development is also increased as the coverage increases. Typically, a high density clear display material has a developer time of 110 seconds compared to a developer time of 45 seconds or less for photographic reflective print materials. Prior art high density clear display materials, when processed, reduce the productivity of the development lab. Further, coating a high coverage of emulsion requires additional drying of the emulsion in manufacturing reducing the productivity of emulsion coating machines. It would be desirable if a clear display material was high in dye density to provide a quality image and had a developer time less than 50 seconds.
Prior art photographic display material use polyester as a base for the support. Typically the polyester support is from 150 to 250 .mu.m thick to provide the required stiffness. A thinner base material would be lower in cost and allow for roll handling efficiency as the rolls would weigh less and be smaller in diameter. It would be desirable to use a base material that had the required stiffness but was thinner to reduce cost and improve roll handling efficiency.